Time-Dependent Dielectric Breakdown of Commercial 1.2 kV 4H-SiC Power MOSFETs

Abstract

Constant-voltage time-dependent dielectric breakdown (TDDB) measurements are performed on recently manufactured commercial 1.2 kV 4H-SiC power metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs) from three vendors. Abrupt changes of the electric field acceleration parameters ( $\gamma $ ) are observed at oxide electric fields ( $E_{ox}$ ) around 8.5 MV/cm to 9 MV/cm for all commercial MOSFETs. Gate leakage currents and threshold voltage shifts are also monitored under different oxide fields ( $E_{ox}= {\mathrm {8 MV/cm}}$ and 10 MV/cm). The results suggest the failure mode under high oxide electric field is modified by impact ionization or Anode Hole Injection (AHI) induced hole trapping. This observation agrees with previously published oxide reliability studies on SiC MOSFETs and suggests that constant-voltage TDDB measurements need to be carefully performed under low oxide fields to avoid lifetime overestimation caused by hole trapping. The extrapolated $t_{63\%}$ lifetimes (times to 63% failures) from TDDB measurements performed at $E_{ox} < {\mathrm {8.5 MV/cm}}$ are longer than 108 hours at 150°C for all vendors. The predicted lifetimes at $E_{ox}= {\mathrm {4 MV/cm}}$ demonstrate more than 105 times increases than the oxide lifetimes reported a decade ago, showing promising progress in SiC technology.

Keywords

• Electron and hole trapping
• impact ionization
• gate oxide reliability
• lifetime
• silicon carbide (SiC) power MOSFETs
• time-dependent dielectric breakdown (TDDB)